GPS portable devices are used by hikers, motorists, safety and military personnel, hunters and many others who may wish to know the exact location of their current position. A GPS device receives positional signals from a number of different satellites surrounding the Earth and uses this information to calculate its position. After the location has been determined, the location is illustrated to the user typically through a display. Some GPS devices also give the user the ability to store his location and track his progress by viewing the display. This display may simply give the coordinates to the user of his current location, or may be more sophisticated and indicate on an electronic map his location.
Presently there are a number of wireless communication devices that allow users to communicate across varying distances. For example, cell phones, two-way radios, internet-ready computers and portable electronics allow one user to communicate to another, either through speech or electronic messages. This communication ability is vital for some people, such as fire rescue personnel, and merely a convenience to others such as old friends who want to catch-up. As GPS data has become more popular, GPS devices have been incorporated into many types of communication devices. For example, some cell-phones also include a GPS receiver allowing the user to locate his own position.
The National Marine Electronics Association (NMEA) has established a standard to transmit location data between GPS devices. This standard is a NMEA sentence and is a self-contained line data. In accordance with NMEA protocol a transceiver will transmit all sentences it is programmed with to a receiver and the receiver selects only the sentences it is programmed to receive. In order for a receiver to read a particular sentence, the beginning of each sentence includes a prefix defining a sentence type and how the sentence should be interpreted. The current NMEA sentences transmit location data using latitude and longitude coordinates represented by degrees and minutes. Along with the location data is a user identification number that indicates what user the location data represents. The NMEA standards currently limit each sentence to 82 characters. Additionally, the NMEA transmission does not allow for a receiving device to request data be resent or indicate back to the transceiver that the sentence was read correctly. One limitation of the current NMEA sentences is that, in addition to length limitations, the data types are also limited. For example, current NMEA sentences only send location data and short identification numbers. Additionally, due to the current format, NMEA sentences do not allow for a user to transmit both location and user identification in the same sentence along with any other information.
There are a few GPS integrated communication devices able to send a unit's location to another device or user through a transceiver that transmits NMEA sentences to the receiver. For example, a GPS device combined with a mobile radio data modem provides the user's location data to a computer located elsewhere. However, this system requires an expensive interface to operate, such as a digital radio interface connected to a computer and running a software application and thus is limited to commercial users. In another example, a GPS device is integrated with a non-licensed personal radio, such as a “walkie-talkie.” These devices only have a limited radio range, making them unsuitable for non-recreational activities. In addition to these two examples, there are other limitations. For example, multiple users cannot track each other using the GPS communication devices, only two users with the same device are able to have each other's locations displayed. Additionally, the transmission ranges are either prohibitively expensive for the average consumer or are so limited in range to be not useful for anything other than casual recreation activities. Finally, the devices are not able to transmit meeting points, waypoints or other information to other users nor allow each user to track his path, speed and estimated time of arrival to the meeting point. These are significant limitations as coordinates that are transmitted vocally to other users may be confused, mistaken or in the military context may be intercepted or overheard by enemy forces. Additionally, as only a limited amount of information is provided to the users, planning, meeting and organizing is much more difficult.